The increasing use of fiber optics for data transmission has extended to undersea instrumentation and submersibles. The fiber optics, in addition to their well known data transmission capabilities, have certain advantages for penetrating a high pressure hull. One in particular is that their small size reduces the problems normally associated with pressure hull penetrations by bulky metal conductors.
One proven approach is disclosed by John T. Redfern in his U.S. Pat. No. 3,825,320 entitled "High-Pressure Optical Bulkhead Penetrator". A cylindrical or tapered plug of glass or cylindrical or tapered bundle of fiber optics is bonded within an accommodatingly shaped bore in a bushing. However, because O-rings and resin adhesives were included to hermetically seal the penetration, possibly, limitations of this design might arise. Each penetrator assembly must be individually tested for pressure integrity in conjunction with the cable it is to be used. Experiences have demonstrated that adhesive boundaries may not be hermetic because most epoxies and polymers at least permit the passage of vapor over a period of time under the extreme pressures encountered in deep ocean applications. In some penetrators "creep" of the adhesive may create leaks. In addition, the smallness of the dimension of the ferrules inserted into the Redfern penetrator may affect alignment of the fibers and compromise the data transfer capability of the penetrator.
The "Fiber Optic Connector Assembly" of Michael A. Dassel, et al., disclosed in U.S. Pat. No. 4,222,629 provides a hermetically sealed coupler. Glass frit bonding fuses the whole arrangement together so that failure of anything from the fiber to the electrooptic conversion element requires that the whole assembly be discarded. If a different electrooptic function is desired, the whole unit must be replaced.
Thus, there is a continuing need in the state-of-the-art for a hermetically sealed high-pressure transparent window adaptable for the transmission of optical data that enhances the light coupling capabilities yet does not overly compromise the wall's structural integrity.